US 4,023,083 A · Torque regulating induction motor system

Abstract

A torque regulating alternating current induction motor control system comprising a motor flux sensing coil arrangement mounted on the induction motor stator for sensing the actual flux produced across the rotor-stator air gap of the motor and deriving a motor flux voltage signal proportional to the actual motor flux. An integrating circuit integrates the voltage signal to obtain a feedback sensed actual motor flux signal representative of the actual air gap flux. An actual torque feedback circuit converts the actual air gap flux and stator current signal to an actual value of torque feedback control signal. A first feedback control loop is responsive to the actual torque feedback control signal and a command value of torque signal and controls the frequency of operation of a power converter supplying the induction motor. A second feedback control loop also responsive to the feedback sensed actual value of flux converts the flux signal into a (V/Hz) voltage control signal for maintaining a substantially controlled value of rotor-stator air gap flux level. The first and second feedback control loops are interconnected and coact to maintain operation of the induction motor at a controlled value of torque. The actual torque feedback circuit includes a flux signal processing circuit for deriving from the output motor flux signals respective direct and quadrature axes flux signal components and combines these signals with direct and quadrature axes motor current signal components in multiplier circuits for multiplying the quadrature axis flux signal by the direct axis motor current signal and for multipyling the direct axis flux signal by the quadrature axis motor current signal. A summing circuit sums the two products to derive an output actual value of torque developd by the induction motor in accordance with the expression T=K(.psi..sub.d i.sub.qs -.psi..sub.q i.sub.ds). The system is designed primarily for use with a three-phase, variable voltage, variable speed, alternating current induction motor intended for traction motor drives and makes available a new and novel actual torque measuring arrangement for use in such systems.

Claims34

Dependent claims

An improved torque regulating control system for an alternating current induction motor having a stator and a rotor spaced from one another by an air gap, said stator including a winding adapted to be excited by a controllable source of electric power so as to produce electromagnetic flux across said air gap, wherein the improvement comprises:

a. motor flux feedback means including means mounted on the motor stator adjacent to said air gap for sensing the actual flux produced across said air gap when said stator winding is excited and means coupled to said flux sensing means for deriving output actual flux signals representative in magnitude and phase of the actual air gap flux;
b. actual torque feedback circuit means responsive to said actual flux signals and to sensed motor stator line currents for deriving an actual value of torque feedback control signal;
c. first feedback control loop means responsive to said actual value of torque feedback control signal for controlling the operation of the power source so as to vary the frequency of stator excitation in a manner that maintains operation of the induction motor at a controlled value of torque;
and
d. second feedback control loop means responsive to said actual flux signals for controlling the power source so as to control the amplitude of stator excitation in a manner that produces a substantially controlled air gap flux level.

2 more elements

A new and improved torque measuring circuit for use in alternating current induction motor control systems including in combination motor flux sensing means for sensing the actual flux induced in the induction motor and deriving output motor flux signals, flux signal processing circuit means coupled to said motor flux sensing means for deriving from said output motor flux signals respective direct and quadrature axes flux signal components .psi..sub.d and .psi..sub.q, motor current sensing means for sensing the motor stator line current and deriving output motor current signals representative thereof, motor current signal processing circuit means coupled to said motor current sensing means for deriving from said output motor current signals respective direct and quadrature axes motor current signals i.sub.ds and i.sub.qs, first multiplier circuit means coupled to said first flux signal processing circuit means and said motor current signal processing circuit means for multiplying said quadrature axis flux signal and said direct axis motor current signal and deriving an output (.psi..sub.q i.sub.ds) representative of their product, second multiplier circuit means coupled to said flux signal processing circuit means and said motor current signal processing circuit means for multiplying said direct axis flux signal and said quadrature axis motor current signal and deriving an output (.psi..sub.d i.sub.qs) representative of their product, and summing circuit means coupled to said first and second multiplier circuit means for summing together the outputs thereof and deriving a resultant output signal T=(.psi..sub.d i.sub.qs -.psi..sub.q i.sub.ds)K representative of the actual value of the torque developed by the motor.

In a torque regulating alternating current induction motor control system comprising torque feedback circuit means for deriving an actual value of torque feedback control signal, power converter circuit means supplying power to said induction motor at a desired stator excitation frequency, and feedback control loop means responsive to said actual value of torque feedback control signal and controlling the operation of said power converter circuit means to vary said stator excitation frequency for maintaining operation of the induction motor at a controlled value of torque, improved torque feedback circuit means comprising motor flux sensing means for sensing the actual flux induced in the induction motor and deriving output motor flux signals, flux signal processing circuit means coupled to said motor flux sensing means for deriving from said output motor flux signals respective direct and quadrature axes flux signal components .psi..sub.d and .psi..sub.qs, motor current sensing means for sensing the motor stator line current and deriving output motor current signals representative thereof, motor current signal processing circuit means coupled to said motor current sensing means for deriving from said output motor current signals respective direct and quadrature axes motor current signals d.sub.d and e.sub.qs, first multiplier circuit means coupled to said flux signal processing circuit means and said motor current signal processing circuit means for multiplying said quadrature axis flux signal and said direct axis motor current signal and deriving an output (.psi..sub.qs i.sub.d) representative of their product, second multiplier circuit means coupled to said flux signal processing circuit means and said motor current signal processing circuit means for multiplying said direct axis flux signal and said quadrature axis motor current signal and deriving an output (.psi..sub.d i.sub.qs) representative of their product, and summing circuit means coupled to said first and second multiplier circuit means for summing together the outputs thereof and deriving an actual value of torque feedback control signal T=(.psi..sub.d i.sub.qs-.psi..sub.qs i.sub.d)K representative of the actual value of the torque developed by the motor.

Dependencies are inferred from the claim text.

Torque regulating induction motor system

Life of this patent

Torque regulating induction motor system

Life of this patent

Abstract

Claims34